> So if I understand correctly it is possible that we've found a small bug
> not in the mesher but in the way some objects are generated ?

Yup, that seems to be the case for the issues shown in your Screenshot_2.jpg . The actual bug is some slight shifting of the shape in closed loft. The amount is pretty small, but it doesn't take very much to cause a slight change in meshing.

Thanks for posting those additional details, I will see if I can tune up closed loft, I'm not sure yet how difficult that will be, it might be a bit hard because the geometry library I'm using is kind of messed up in this particular area. But I'll give it a try...

The one shown in your Screenshot_1.jpg (the low poly one) is a different problem though - in that case there were n-gons being created like this:



So there are some rectangular shaped n-gons there made up of 6 points.

Then since you had your output set to "Quads and Triangles", it would triangulate those and cause the asymmetry. It will be difficult in general to ensure that the triangulation of any n-gon will end up exactly symmetrical to another n-gon across some interior surface line.

However, I have improved the mesher for the next beta to solve at least this case that you show here. Previously it would convert any n-gon into triangles, but with the next beta it will examine the n-gon and if the n-gon is made up of a strip of regular quads as it happens to be in this case, then it will break the n-gon into those quads instead of triangulating it. There are still asymmetries if you use triangles only, but this helps out a bit for the quads + triangles case.

- Michael

>> However, I have improved the mesher for the next beta to solve at least this case that you show here. Previously it would convert any n-gon into triangles, but with the next beta it will examine the n-gon and if the n-gon is made up of a strip of regular quads as it happens to be in this case, then it will break the n-gon into those quads instead of triangulating it. There are still asymmetries if you use triangles only, but this helps out a bit for the quads + triangles case.

- Sounds good ! Thanks.

It seems like it is pretty common to get some ngons like this. So this helps to produce more quads and less triangles.

- Michael

One thing I found. When meshing a object created via revolution, setting the "Angle" field to a number that can smoothly divide into 360 seems to produce symmetrical results. Fractional angle values seem to lead to messier meshes.

Hi Michael,

would it be possible to get a quad only export?
I usually continue to work on the models in subd modellers, and to have triangles there is a pain,
so at the moment I have to manually turn triangles into quads...

Thor

Hi Thor, unfortunately that is not going to be easy for me to do anytime very soon. The underlying surfaces themselves go naturally into quads, but when there are trim curves on the surface (which happens after some types of cutting operations such as booleans), the "surface quad" basically gets cut by arbitrary curves. It is very difficult to take arbitrary trim curves and then try to get quads out of them.

- Michael

Yes, IMO, that's the paradox of using NURBS modelers, generating a mesh that's "polygon app friendly".

It is very difficult, if not impossible...

Typically I use NURBS generated objects as "statics" in my scenes; buildings, furniture, pretty much anything that isn't animated or doesn't require clean topology.

Another option is to load the resultant mesh in to Silo 3D or TopoGun and recreate the hi-res NURBS object into a smaller, all-quad topology. Unfortunately, that just feels like doing extra work to me but it's certainly an option (and mostly the reason why a tool like TopoGun exists...)

-Will

Hi Bernard - it looks like I have managed to fix this problem with closed lofts for the next beta.

- Michael